I am probably a bigger Apple critic than most, but I genuinely don’t understand the commonly stated sentiment that Apple is bad at fractional scaling. I’ve been running 27” 4K monitors at “looks like 1440p” scaling on my MBPs for years, and I literally cannot tell the difference in quality between the built in display and my monitors. Is there some particular app or use case where it’s more noticeable?
Apple only supports pixel-perfect rendering at 1x or 2x scales, if you choose anything inbetween then they render at a non-native resolution then resample the result to fit the displays actual resolution. That has two effects, the scaling means the results aren't as sharp as they could be, and the oversampled rendering means there's a performance overhead (in your case the GPU is actually rendering 5K internally, which is then scaled down to 4K). The latter was more of an issue with Intel Macs, the Apple Silicon GPUs are generally beefy and efficient enough to take it in stride.
If you don't notice it then that's fine, but some people do, particularly if they are used to Windows' pixel-perfect fractional scaling.
Even on an Intel Mac with a discrete GPU, fractional scaling is rarely a problem. I typically run my trashcan Mac Pro (low-end D300 GPUs) at 4K/1440p, and only a few problems come to mind:
• Microsoft Remote Desktop (with "Optimize for Retina displays" enabled and RDP host settings optimized for quality) is usable and looks good, but things that rapidly change large sections of the display, like dragging windows around, have noticeable lag. Though this lag is generally only reduced, not eliminated, at native resolutions, so changing modes in this case is rarely worthwhile, and the Windows applications I use most (Visual Studio, JetBrains Rider, and Windows Terminal) run well enough that I choose to work via 1440p-like Remote Desktop 99% of the time even when a local connection is only a KVM switch away.
• Playing back 60 FPS videos in mpv with high quality presets and scaling algorithms drops frames. Default settings and lower frame rate videos both work fine, and in light of Retina superscaling, the quality difference is negligible, so I change mpv settings rather than scaling settings in this case.
• While not a performance problem, displays from OSes designed with pixel-perfect rendering in mind (e.g., classic Mac OS, NeXTSTEP) look bad at higher-than-VGA resolutions. The only scenario where I typically switch to another scaling mode is when emulating these.
Yeah, I understand how it works, I just don’t notice any real-world difference. I never saw any evidence that Intel Macs were slower at it either; I think that part is just an oft-repeated myth.
However, another reply said the built-in display is likely fractionally scaled as well; I hadn’t considered that at all, so I’ll have to set it to 2x if so, and see if I notice a difference.
